1. Field
Example embodiments of the present invention relate to a method of forming carbon nanotubes, for example, a method of simply and easily forming nitrogen-doped or other Group V-doped, single-walled carbon nanotubes.
2. Description of the Related Art
A carbon nanotube may be a carbon allotrope and may be a material in which one carbon atom may be combined with other carbon atoms in a honeycomb shaped tube. The diameter of the honeycomb shaped tube may only be a few nanometers. Carbon nanotubes may have improved mechanical characteristics, electrical selectivity, field emission characteristics, and/or relatively highly efficient hydrogen storing medium characteristics.
A carbon nanotube may be a rolled graphite sheet forming a tube having a nano-size diameter, and may have a sp2 bonding structure. A carbon nanotube may have electrical conductor characteristics or semiconductor characteristics according to the rolling angle and the shape of the graphite sheet. Carbon nanotubes may be classified into single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs), according to the number of carbon nanotubes that constitute a wall. Also, a bundle form, in which a plurality of SWNTs is gathered, may be known as a rope nanotube.
Carbon nanotubes may be manufactured using a high synthetic technique, for example, a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, a Thermal Chemical Vapor Deposition (TCVD) method, an electrolysis method, or a flame synthetic method.
Due to their improved electrical characteristics, carbon nanotubes may be used for manufacturing semiconductor devices, for example, CMOS devices. In general, a semiconductor manufacturing process and a semiconductor integration process must be performed at a temperature below about 500° C. to reduce product defects. However, when carbon nanotubes are grown at a temperature below about 500° C. using a conventional carbon nanotube synthetic method, defective carbon nanotubes may be grown because many impurities, for example, amorphous carbon, may be generated during the synthetic process. The defective carbon nanotubes may degrade the characteristics and performance of a semiconductor device.
Also, to manufacture a CMOS using a carbon nanotube-based transistor, an n-type and a p-type SWNT must be manufactured. However, a technique that may dope a donor during the SWNT synthetic process has not been developed. In general, an intrinsic SWNT may have a p-type characteristic by surface adsorption of oxygen in the air. Also, a technique that may synthesize the n-type SWNT has not been developed. To solve this problem, a method of manufacturing an n-type transistor by adsorbing an alkali metal, for example, amine or potassium K having an electron-donating group on a surface of the SWNT, may have been attempted. However, the doping material adsorbed on the surface of the SWNT may be unstable, that is, the doped material may break away at any time. Therefore, the doping of a material by adsorption on the surface of the SWNT remains an unreliable device characteristic.